A circa-2014 layout shows several modifications that have been made since 1988. A fourth anchor, J.C. Penney, was built onto the east end in 1994-1995. Dillard's established a "double-header" in 2002 and Foley's was "Macy-ated" in 2006. 

This snapshot -and the two that follow- are contemporary views of PENN SQUARE. They reflect renovations done between 1999 and 2013. The mall's main entrance is seen here.
Photo from www.simon.com / Simon Property Group

In this image, we see the bi-level Center Court, its escalators and glass-enclosed elevator.
Photo from www.simon.com / Simon Property Group

In this image, we see the main (east-west) shopping concourse. On the lower left are Chico's and Ann Taylor. American Eagle Outfitters and Aldo Shoes nameplates are seen on the Upper Level. 
Photo from www.simon.com / Simon Property Group

Lastly, we have a contemporary aerial view of Oklahoma's oldest -and largest- mall. The complex covers approximately 1,083,900 leasable square feet and contains 145 stores and services.

Photo from Wikipedia / Dave Morris